Detect Code Signing Policy Modification in Sumo Logic CSE
Adversaries may modify code signing policies to enable execution of unsigned or self-signed code. On Windows, this includes enabling TESTSIGNING boot mode via bcdedit.exe, disabling Driver Signature Enforcement (DSE) by modifying the g_CiOptions kernel variable (typically via a BYOVD exploit), or changing registry keys that control signed DLL enforcement such as RequireSignedAppInit_DLLs. On macOS, adversaries disable System Integrity Protection (SIP) using csrutil disable from Recovery Mode. Threat actors including APT39, BlackEnergy, Hikit, Pandora, and Turla have used these techniques to load unsigned rootkit drivers and persist with kernel-level access.
MITRE ATT&CK
- Tactic
- Defense Evasion
- Technique
- T1553 Subvert Trust Controls
- Sub-technique
- T1553.006 Code Signing Policy Modification
- Canonical reference
- https://attack.mitre.org/techniques/T1553/006/
Sumo Detection Query
_sourceCategory=windows/*
| where _sourceName matches "*WinEventLog*" or _sourceName matches "*Sysmon*"
| parse "EventCode=*]" as EventCode nodrop
| parse "EventID=*]" as EventCode nodrop
| where EventCode in ("1", "13", "4688", "4657")
| parse field=_raw "<Data Name='Image'>*</Data>" as image nodrop
| parse field=_raw "<Data Name='CommandLine'>*</Data>" as command_line nodrop
| parse field=_raw "<Data Name='TargetObject'>*</Data>" as target_object nodrop
| parse field=_raw "<Data Name='Details'>*</Data>" as reg_details nodrop
| parse field=_raw "<Data Name='NewProcessName'>*</Data>" as image nodrop
| parse field=_raw "<Data Name='CommandLine'>*</Data>" as command_line nodrop
| parse field=_raw "<Data Name='ObjectName'>*</Data>" as target_object nodrop
| parse field=_raw "<Data Name='NewValue'>*</Data>" as reg_details nodrop
| parse field=_raw "Computer=\"*\"" as hostname nodrop
| parse field=_raw "<Data Name='User'>*</Data>" as username nodrop
| parse field=_raw "<Data Name='SubjectUserName'>*</Data>" as username nodrop
| where (
(EventCode in ("1", "4688")
and matches(toLowerCase(image), ".*bcdedit\.exe.*")
and (
matches(toLowerCase(command_line), ".*testsigning.*")
or matches(toLowerCase(command_line), ".*nointegritychecks.*")
or matches(toLowerCase(command_line), ".*bootdebug.*")
or matches(toLowerCase(command_line), ".*safeboot.*")
)
)
or
(EventCode in ("13", "4657")
and (
matches(target_object, "(?i).*RequireSignedAppInit_DLLs.*")
or matches(target_object, "(?i).*LoadAppInit_DLLs.*")
or matches(target_object, "(?i).*HypervisorEnforcedCodeIntegrity.*")
or matches(target_object, "(?i).*EnableVirtualizationBasedSecurity.*")
or matches(target_object, "(?i).*RequirePlatformSecurityFeatures.*")
or matches(target_object, "(?i).*\\Control\\CI\\.*")
or matches(target_object, "(?i).*\\Control\\CodeIntegrity.*")
)
)
)
| eval detection_type = if(EventCode in ("1","4688"), "BCD_Policy_Modification",
if(EventCode in ("13","4657"), "Registry_CISigning_Modification", "Unknown"))
| eval severity = if(
matches(toLowerCase(command_line), ".*nointegritychecks.*on.*"), "critical",
if(matches(toLowerCase(command_line), ".*testsigning.*on.*"), "high",
if(matches(target_object, "(?i).*HypervisorEnforcedCodeIntegrity.*"), "critical",
if(matches(target_object, "(?i).*RequireSignedAppInit.*"), "high", "medium"))))
| eval testsigning_enabled = if(matches(toLowerCase(command_line), ".*testsigning.*") and matches(toLowerCase(command_line), ".*\\bon\\b.*"), "true", "false")
| eval hvci_modified = if(matches(target_object, "(?i).*HypervisorEnforcedCodeIntegrity.*"), "true", "false")
| fields _messagetime, hostname, username, image, command_line, target_object, reg_details, detection_type, severity, testsigning_enabled, hvci_modified
| sort by _messagetime descSumo Logic detection for T1553.006 consuming Windows Security Event Log and Sysmon operational logs. Parses XML event fields inline to extract image path, command line, and registry target object. Matches bcdedit.exe process events (Sysmon EID 1 / Security EID 4688) with signing-bypass arguments, and registry set-value events (Sysmon EID 13 / Security EID 4657) targeting DeviceGuard, HVCI, RequireSignedAppInit_DLLs, CI, and CodeIntegrity keys. Severity and detection type computed via inline eval.
Data Sources
Required Tables
False Positives & Tuning
- Enterprise driver development labs where TESTSIGNING is a routine part of the internal kernel driver build-test-sign cycle, generating high volumes of bcdedit events on known developer machines
- Helpdesk or IT admin accounts running bcdedit to recover systems stuck in boot loops or to disable Secure Boot for OS reinstallation on endpoint hardware
- Endpoint security product deployments (e.g., CrowdStrike, Carbon Black) that write to DeviceGuard or CI registry paths during installation or sensor update workflows
Other platforms for T1553.006
Testing Methodology
Validate this detection against 5 adversary techniques from Atomic Red Team. Each test below lists the behaviour to exercise and the telemetry you should expect to see. Executable commands and cleanup steps are available with Pro.
- Test 1Enable TESTSIGNING Boot Mode via bcdedit
Expected signal: Sysmon Event ID 1: Process Create with Image=C:\Windows\System32\bcdedit.exe, CommandLine='bcdedit /set testsigning on'. Security Event ID 4688 (with process command line auditing enabled) with same details. Note: no additional event is generated when TESTSIGNING takes effect at next reboot — the bcdedit process event is the only log entry.
- Test 2Disable Driver Signature Enforcement via nointegritychecks
Expected signal: Sysmon Event ID 1: Process Create with Image=bcdedit.exe and CommandLine containing 'nointegritychecks on'. Security Event ID 4688 if process command line auditing is enabled. Microsoft-Windows-Kernel-Boot/Operational Event ID 16 will show the changed boot configuration at next boot cycle.
- Test 3Disable RequireSignedAppInit_DLLs via Registry
Expected signal: Sysmon Event ID 13: Registry Value Set with TargetObject='HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Windows\RequireSignedAppInit_DLLs', Details='DWORD (0x00000000)'. Sysmon Event ID 1: Process Create for reg.exe with full command line. Security Event ID 4657 if object access auditing is configured for registry keys.
- Test 4Disable Hypervisor-Protected Code Integrity (HVCI) via Registry
Expected signal: Sysmon Event ID 13: Registry Value Set with TargetObject containing 'DeviceGuard\HypervisorEnforcedCodeIntegrity', Details='DWORD (0x00000000)'. Sysmon Event ID 1 for reg.exe process. Security Event ID 4657 (if object access auditing enabled). At next reboot: Windows Event Log Microsoft-Windows-DeviceGuard/Operational will show HVCI enforcement status change.
- Test 5macOS System Integrity Protection Status Check and Disable Simulation
Expected signal: macOS Unified Log (ULS): process execution of csrutil with 'disable' argument. EDR telemetry (if macOS endpoint agent deployed): process creation event for /usr/bin/csrutil with arguments 'disable'. The command will fail with 'csrutil: failed to modify system integrity configuration. This tool needs to be executed from Recovery OS.' which itself is a detectable signal.
References (13)
- https://attack.mitre.org/techniques/T1553/006/
- https://docs.microsoft.com/en-us/windows-hardware/drivers/install/the-testsigning-boot-configuration-option
- https://docs.microsoft.com/en-us/windows-hardware/drivers/install/installing-an-unsigned-driver-during-development-and-test
- https://developer.apple.com/documentation/security/disabling_and_enabling_system_integrity_protection
- https://blog-assets.f-secure.com/wp-content/uploads/2019/10/15163408/BlackEnergy_Quedagh.pdf
- https://web.archive.org/web/20210920172620/https://www.fireeye.com/blog/threat-research/2012/08/hikit-rootkit-advanced-persistent-attack-techniques-part-2.html
- https://unit42.paloaltonetworks.com/acidbox-rare-malware/
- https://github.com/hfiref0x/TDL
- https://www.loldrivers.io/
- https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1553.006/T1553.006.md
- https://github.com/SigmaHQ/sigma/search?q=testsigning
- https://learn.microsoft.com/en-us/windows/security/threat-protection/device-guard/enable-virtualization-based-protection-of-code-integrity
- https://www.trendmicro.com/en_us/research/21/d/iron-tiger-apt-updates-toolkit-with-evolved-supply-chain-attack-capabilities.html
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